A simple surgical procedure destroying certain nerves in the kidney can sharply reduce blood pressure in patients whose hypertension cannot be controlled with conventional medications, researchers said Wednesday.
The study was conducted on 52 patients whose blood pressure averaged 178/96, despite the fact that they were taking five hypertension medications. On average, their blood pressure dropped by 32/12, while a control group of 54 patients receiving only drugs showed no change.
"Those blood pressure reductions are pretty remarkable," said Dr. Douglas Weaver, division head of cardiovascular medicine at the Henry Ford Health System in Detroit, who was not involved in the study. "Those patients had been given everything and had not responded.... Did they prove that this [should go into the clinic]? No, the study is far too small. But they have shown that here is a way we could potentially lower blood pressure."
Dr. Suzanne Oparil, a hypertension specialist at the University of Alabama at Birmingham who also was not involved in the research, noted that "this is an extremely important study. We did work in the 1980s that showed that this prevents hypertension in animals, but had no way of translating it into humans. There is an enormous clinical need for this kind of approach."
An estimated 75 million Americans have high blood pressure, defined as a pressure of 140/90 millimeters of mercury or higher. Anything between 120/80 and 140/90 is considered borderline high. High blood pressure is one of the leading causes of heart disease and stroke.
Some studies have shown that reducing the systolic blood pressure (the top number) by only 6 millimeters of mercury can reduce the relative risk of stroke by 35% to 40% and the relative risk of a heart attack by 20% to 25%.
But an estimated 15% of those with high blood pressure are unable to control it, despite taking three or more medications. It is those people at whom the new treatment is aimed.
Researchers have known for decades that the sympathetic nervous system, which plays a role in the body's "flight or fight" response, helps regulate blood pressure. Early attempts to control it with surgery produced severe side effects, and the efforts were abandoned when the first effective anti-hypertensive drugs became available.
More recently, Ardian Inc. of Mountain View, Calif., has developed a system in which a small catheter is threaded through the groin and to the kidney, where radiofrequency energy is used to destroy targeted nerves more precisely.
Dr. Murray D. Esler of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, led a trial of the device. The results were reported at a Chicago meeting of the American Heart Assn. and online in the journal Lancet.
The researchers found that only five of the 52 patients in the study did not respond to the kidney treatment. For the rest, the mean systolic blood pressure after treatment was 146, and for 39% of those patients it dropped below 140, Esler said. The patients are still taking drugs, but some have been able to reduce their doses.
The patients have so far been followed only for six months. But Esler noted that some people in an earlier trial of the same procedure have now been followed for as long as two and a half years and their blood pressure has not gone back up.
The team found no acute damage from the surgery, and no significant side effects, he said.
The procedure takes about 40 to 60 minutes and would probably cost about $13,500, according to Ardian. An overnight hospital stay would probably be necessary.
Ardian has been in discussions with the Food and Drug Administration about the procedure, the company said, and will probably begin a larger trial in the U.S. next year.
For his part, Esler envisions future trials on patients with less severe hypertension in which the treatment would result in a cure, not just improvement.
"We're slowly moving toward that, but to cure hypertension is probably still a dream," he said.